Identification of a soluble interleukin-8 inhibitor in the supernatant of polymorphonuclear leukocytes

Interleukin-8 (IL-8) plays a crucial role in the pathogenesis of inflammato ry and hyperproliferative diseases in various organs. The purpose of the pr esent investigation was to establish whether there is any naturally occurri ng inhibitor of IL-8. Here we demonstrate that an IL-8 inhibitor (IL-8INH) is present in the supernatant of polymorphonuclear (PMN) leukocytes. The re lease of IL-8INH could be increased by stimulating the PMN leukocytes by co ncanavalin A. IL-8INH blocks the IL-8-induced chemotaxis and Candida albica ns killing activity of PMN leukocytes and epidermal cells in vitro, and IL- 8-induced neutrophil infiltration in the mouse ear in vivo. The mechanism o f action of IL-8INH involves blocking of I-125-IL-8 binding to the IL-8 rec eptor. Binding of I-125-IL-8 to neutrophils could not be displaced by the I L-8INH, however, preincubation of I-125-IL-8 with IL-8INH increased binding inhibition, suggesting an interaction between IL-8 and the inhibitor. Cros slinking of I-125-IL-8 to IL-8INH shows that IL-8INH binds specifically to I-125-IL-8, and the IL-8INH protein has an apparent molecular weight of 52 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The parti al purification of the IL-8INH on DEAE-Sephadex anion-exchange chromatograp hy column also suggests a 50-60-kDa inhibitor protein which blocks IL-8-ind uced effects on neutrophils by binding to IL-8. (C) 1998 Elsevier Science B .V. All rights reserved.